Orifice Region Research Articles

Influence of fuel properties on internal nozzle flow development in a multi-hole diesel injector

Fuel physical properties are known to influence in-nozzle flow behavior, in turn affecting spray formation in internal combustion engines. A series of 3D simulations was performed to model the internal nozzle flow in a five-hole mini-sac diesel injector. The goal of the study was to evaluate the behavior of two gasoline-like fuels (full-range naphtha and light naphtha) and compare them against n-Dodecane, selected from a palette used as a diesel surrogate. Simulations were carried out using a multi-phase flow representation based on the mixture model assumption with the Volume of Fluid (VOF) method, and including cavitation effects by means of the Homogeneous Relaxation Model (HRM). Validated methodologies from our previous studies were employed to account for full needle motion. Detailed simulations revealed the influence of the fuel properties on injector performance, injected fuel energy and propensity to cavitation. The three fuels were compared with respect to global parameters such as mass flow rate and area contraction coefficients, and local parameters such as pressure and velocity distribution inside the sac and orifices. Parametric investigations were also performed to understand the fuel response to changes in the fuel injection temperature, injection pressure, and geometry details. Cavitation magnitude was observed to be strongly associated with the values of saturation pressure. Owing to their higher volatility, the two gasoline-like fuels were observed to cavitate more than n-Dodecane across all the investigated conditions. While at full needle lift cavitation was reduced for all fuels, during the injection transients the gasoline-like fuels showed more propensity to cavitate inside the orifice and seat regions. This is expected to have a profound influence on nozzle erosion. Although full-range and light naphtha have lower densities compared to n-Dodecane, owing to their lower viscosity, the mass flow rate differences between the naphtha fuels and n-Dodecane were small. The analysis of fuel energy content showed that the higher lower heating value (LHV) of light naphtha helped compensate for the slightly lower total delivered mass.

Colonoscopic Visualisation of Benign Polyps in the Appendiceal Region

Detection of pre malignant polyps is an important objective during colonoscopy Careful attention is crucial to fully evaluate all luminal orifices of the colon In this case report we report four cases of pre malignant polyps in the appendiceal orifice region Herewith we give emphasis to the importance of visualising the whole colon including the appendiceal orifice region during colonoscopy

Case Report: Intraoperative Management Using Inferior Based Rotation Flap of Sternocleidomastoid Muscle for Chyle Fistula

Chyle fistula is one of the complications of neck dissections. Although immediate surgical repair seems to be the best choice when chyle leakage is observed during the operation, some operators can be embarrassed when chyle leakage is heavy and not controlled during surgery. In this case, chyle leakage was occurred after extensive resection of lymph nodes in left level IV, and was not controlled in any way. The clavicular head of sternocleidomastoid muscle was dissected and inferior-based muscular flap was rotated to cover the suspected region of fistula orifice. Amount of drainage was checked less than 20 ml per day in the following days, and drain tube was taken out on the 3rd postoperative days. We present the technique using the inferior based sternocleidomastoid muscle flap for intraoperative management of chyle leakage not easily controlled.

Vortex convection in the flow-excited Helmholtz resonator

Vorticity convection as well as its excitation to a Helmholtz resonator is studied numerically. Convection velocities of both the concentrated vortical structure and the total distributed vorticity in the orifice region are calculated. Results indicate that the vortex convection velocity is the more useful one in controlling the oscillation frequency. The excitation pressure from the vortical flow is found almost in phase with the fluctuation of the total circulation in the orifice region. This helps us to deduce that vorticity accumulation in the opening region and its relatively simultaneous efflux, due to the shear layer rolling-up into a vortex, are responsible for the pressure fluctuation that excites the acoustic mode of the cavity. It is found that the frequency characteristics can be significantly varied by the system damping. Increasing the damping leads to a reduction in the range of the Strouhal number of oscillation, which is associated with the disappearing lock-in effect in frequency. The dependence of the vortex convection velocity and the critical Strouhal number for the maximum oscillation on damping is also shown.

Prospective randomized trial comparing laparoscopic transabdominal preperitoneal (TAPP) and laparoscopic totally extra peritoneal (TEP) approach for bilateral inguinal hernias

IntroductionBilateral inguinal hernias form a part of the complex spectrum of weakness in the region of the myopectineal orifice. Laparoscopic surgery is one of the standard approaches for bilateral hernias. We describe the results of a randomized trial that was undertaken to compare and evaluate TAPP and TEP repair for bilateral inguinal hernias. MethodsSixty patients were randomized into two groups. Group I (TAPP) and Group II (TEP) were compared in terms of procedure related variables, conversion, post-operative recovery and complications. Analysis was done using SPSS software version 17. ResultsSeventy-seven patients were assessed for fitness to include in the study. Seventeen patients had to be excluded due to either not meeting the inclusion criteria's or for not giving consent. The median age (52yrs) was comparable in both groups. In Group II (TEP) mean operating time was 120.89 ± 29.28 min compared to 108.16 ± 16.10 min in Group I (TAPP). Post-operative pain scores were less in Group I(TAPP) at all levels of recording (8 h–48 h), though most patients required injectable analgesic for 32 h in both groups (p-value 0.029). Subcutaneous emphysema was more commonly noted in the Group II (TEP) (p-value 0.038). In Group I (TAPP) mean hospital stay was 52.0 ± 14.21 h while in Group II (TEP) it was 52.29 ± 9.36 h (p-value 0.427). Mean time for return to work was 11.8 ± 2.35 days in Group I (TAPP) and 12.41 ± 2.22 days in Group II (TEP) (p-value 0.339). ConclusionThe procedures though different in approach were quite similar in outcome. Mean operating time was increased in the TEP repairs along with immediate post-operative pain scores. The pattern of some complications like subcutaneous emphysema was significantly more in the TEP group while minor vascular injury though not significant was different in both groups. The indirect cost incurred from consumables did not vary other than need for more tacks in the TAPP group.

Endoscopic management of salivary gland obstructive diseases in patients with Sjögren's syndrome.

To evaluate, on the basis of our clinical experience, the reliability of an endoscopic approach to the management of obstructive salivary diseases related to Sjögren's syndrome. A retrospective review of all patients affected by Sjögren's syndrome who were followed up at the Maxillo-Facial Unit of the Second University of Naples Hospital and referred from the Reumatology Unit of the same hospital from September 2007 to July 2012 for chronic obstructive sialadenitis unresponsive to medical therapy. A total of 34 patients (29 women and 5 men) were recruited for this study. After the detection of the impaired gland, under local anesthesia with lidocaine 2% to the orifice region and a gradual dilation of the duct orifice, the diagnostic unit was introduced into the duct and was advanced forward until reaching the ductal system, with continuous lavage with isotonic saline solution. The plaques were washed out, and any strictures were dilated. Mucus plugs and debris were removed with irrigation or with a forceps if necessary. Our cohort included 34 patients with a mean age of 51.76 years. A total of 60 parotid glands and 25 submandibular glands were explored and treated. Strictures were found in 38 glands (38 of 85; 45%), mucus plugs in 47 glands (47 of 85; 55%), mucus plugs and strictures together in three glands (3 of 85; 4%), and kinks in two glands (2 of 85; 2%). In 32 parotid glands (32 of 60; 53%) the Stensen duct was affected, in two (2 of 60; 3%) only secondary ducts, and in 18 (18 of 60; 30%) both. In submandibular glands explored, strictures and mucus plugs were mainly observed in Wharton ducts. Symptomatic improvement was achieved in 29 patients (29 of 34; 85%), in a follow-up period ranging from 5 months to 3 years. Interventional sialoendoscopy is a viable technique to treat acute symptomatology in patients with obstructive salivary gland diseases related to Sjögren's syndrome and refractory to conventional management.

Simulation of the electric field distribution in the electrode system of a device forming a high-voltage gas discharge

We propose a model of the electric field distribution in the electrode system of a gas-discharge device. The possibility of application the method of conformal mapping of a function of a complex variable for describing analytically the form of the distribution of equipotential lines of the field in the region of the circular orifice in the anode of the gas discharge device is demonstrated. The method for obtaining a system of parametric equations for determining the equipotential lines and field lines is described. We obtain the theoretical maps of the electric field distribution, which make it possible to determine their relation with the electrophysical parameters of the electrode system of the device.

Theoretical Model of a Lanthanum Hexaboride Hollow Cathode

A model to predict the plasma properties inside a thermionic hollow cathode as a function of operational conditions and geometry is presented. The hollow cathode features a lanthanum hexaboride (LaB6) insert, which is capable of emitting current densities as high as $10^{5}~\mathrm{Am}^{-2}$ at temperatures of $\sim 1900$ K, along with a tantalum orifice plate located at the downstream end of the cathode tube. The model self-consistently computes the plasma parameters in both the emitter and orifice regions. A simple semiempirical relation is suggested to evaluate the plasma penetration depth in the cathode interior, which is of primary importance to establish the plasma conditions. The heat transfer mechanisms and the related temperature gradients along the cathode are evaluated with the aid of a dedicated thermal model, which is coupled to the plasma model and accounts for temperature-dependent material properties. A parametric study of the cathode performance was conducted to assess the dependence of the power consumption and operational lifetime on discharge current and mass flow rate, as well as on the geometry. The results are in good agreement with both theoretical and experimental trends found in the literature as well as with experimental data collected by Alta. Further developments will include a deeper investigation into the cathode erosion phenomena, along with a broader comparison with empirical data.

Postpartum urinary retention secondary to suture obliteration of the urethral orifice: A complication of home delivery conducted by an untrained birth attendant

Postpartum urinary retention (PPUR) secondary to suture obliteration of the urethral orifice by a traditional birth attendant (TBA) is a condition that may not have been heard of in modern day obstetric practice and has certainly not been reported before in our locality. Several risk factors to developing PPUR have been reported. However, following a careful search of the literature, there was no documented case of PPUR secondary to closure of the urethral orifice by TBA. We report a rare case of a 23-year-old multipara who had spontaneous vaginal delivery that was supervised by a TBA at home. She presented 3 days later with complaints of inability to pass urine, abdominal pain, abdominal swelling, and dribbling of urine on straining. She was evaluated and found to have a distended urinary bladder up to the level of the umbilicus. Pelvic examination revealed a vestibule that was almost completely obliterated up to the urethral orifice with continuous surgical silk suture. The vaginal orifice was also partially obliterated. Urine was noticed to be dribbling from the region of the urethral orifice on straining. Lochia was normal. About 2 L of clear urine was drained from the urinary bladder following cutting of the silk suture and passage of an indwelling size 16F Foley's catheter. The uterus was contracted to 16 weeks pregnancy size following catheterization. She had successful bladder training and was discharged 5 days later.

Role of steroidal anti-inflammatory agent prior to intracorporeal lithotripsy under local anesthesia for ureterovesical junction calculus: A prospective randomized controlled study.

Objective:The objective of the following study is to assess the effect of steroidal anti-inflammatory agent on the outcome of ureterorenoscopic lithotripsy (URSL) for ureterovesical junction (UVJ) calculus.Settings and Design:This was a prospective randomized controlled study conducted at the Department of Urology, Regional Institute of Medical Sciences, Imphal.Subjects and Methods:One hundred and twenty-six patients requiring ureteroscopic lithotripsy for UVJ calculus were randomly assigned into two groups. The study group received tablet deflazacort 30 mg once a day for 10 days prior to the procedure, whereas the control group did not receive such treatment. Parameters with respect to the outcome of the procedure were recorded for all patients in both groups.Statistical Analysis Used:Fisher's exact and independent t-test was used to compare the outcome between the groups where P < 0.05 was considered to be statistically significant.Results:There was significant statistical difference (P - 0.016) on the endoscopic appearance of the region of ureteric orifice in patients receiving steroidal anti-inflammatory agent compared with control. Severe procedure related pain and mean operative time was less in the study group compared to control (P - 0.020 and 0.031, respectively). Re-treatment rates in the study group were lower than the control group (4.76% vs. 17.46%) and found to be statistically significant (P - 0.044). It is found that computed tomography (CT) appearance (r - 0.399) and stone size (r - 0.410) strongly correlate with the endoscopic findings of the region of UVJ (P - 0.001).Conclusions:Inflamed and or obliterated ureteric orifice is the major constraints for stone clearance at ureterovesical junction. The present study showed the administration of tablet deflazacort (a steroidal anti-inflammatory agent) significantly improves the outcome of URSL under local anesthesia. We strongly recommend its use prior to URSL for UVJ calculus, especially for stone size ≥10.24 mm and on CT evidence of prominent soft tissue swelling at the UVJ.

Global Numerical Model for the Assessment of the Effect of Geometry and Operation Conditions on Insert and Orifice Region Plasmas of a Thermionic Hollow Cathode Electron Source

AbstractThermionic hollow cathodes have been widely used in wide variety of areas such as spacecraft electric propulsion systems, material processing and lasers for more than half a century as efficient electron sources. Especially in electric propulsion systems, hollow cathodes are being used as electron sources for propellant ionization and ion beam neutralization. Moreover, it is also a promising candidate for utilization as a stand‐alone propulsion system in microsatellites or nanosatellites due to its small physical size, low power consumption and ease of operation. On the other hand, the small geometry of the typical orificed hollow cathodes makes the plasma diagnostics difficult which is why numerical studies become important for understanding the driving physical processes behind their operation, and the effects of the geometry and the operation parameters on cathode performance. In this paper, a global numerical model for the insert and orifice plasma of a hollow cathode is presented where volume averaged plasma parameters are considered for both regions. The results of this study show that the developed model can be used for designing and sizing orificed hollow cathodes as comparisons with the results of experimental and other numerical studies are in good agreement with the ones obtained from the developed model. (© 2014 WILEY‐VCH Verlag GmbH &amp; Co. KGaA, Weinheim)

Distribution of CD4(pos) -, CD8(pos) - and regulatory T cells in the upper and lower gastrointestinal tract in healthy young subjects.

The gastrointestinal immune system is involved in the development of several autoimmune-mediated diseases, including inflammatory bowel disease, multiple sclerosis, and type 1 diabetes mellitus. Alterations in T-cell populations, especially regulatory T cells (Tregs), are often evident in patients suffering from these diseases. To be able to detect changes in T-cell populations in diseased tissue, it is crucial to investigate T-cell populations in healthy individuals, and to characterize their variation among different regions of the gastrointestinal (GI) tract. While limited data exist, quantitative data on biopsies systematically drawn from various regions of the GI tract are lacking, particularly in healthy young humans. In this report, we present the first systematic assessment of how T cells—including Tregs—are distributed in the gastrointestinal mucosa throughout the GI tract of healthy young humans by means of multi-parameter FACS analysis. Gastroduodenoscopy and colonoscopy were performed on 16 healthy volunteers aged between 18 and 32. Biopsies were drawn from seven GI regions, and were used to determine the frequencies of CD8+-, CD4+- and Tregs in the gastrointestinal mucosa by means of multi-parameter FACS analysis. Our data show that there is significant variation in the baseline T-cell landscape along the healthy human gastrointestinal tract, and that mucosal T-cell analyses from a single region should not be taken as representative of the entire gastrointestinal tract. We show that certain T-cell subsets in the gastrointestinal mucosa vary significantly among regions; most notably, that Tregs are enriched in the appendiceal orifice region and the ascending colon, and that CD8pos T cells are enriched in the gastric mucosa.

A Reduced-Order Model for Thermionic Hollow Cathodes

A reduced-order numerical model describing the plasma in an orificed hollow cathode is presented as a quick tool for the design of thermionic cathodes. A time-independent, volume-averaged model is developed to determine plasma properties, wall temperatures, and cathode lifetime without requiring experimental data as input. A system of particle and energy balance equations is numerically solved without invoking a Saha-type equilibrium under the hypothesis of a direct-impact ionization process. Further, a lumped-parameter thermal model is coupled with the plasma model to estimate the temperature profile along the cathode axis and the emitter lifetime. The obtained results capture most of the characteristic features of this class of hollow cathodes as compared with the available experimental data. In addition, the model gives insight into the most important power deposition processes affecting the emitter and orifice regions. The effect of the geometry on both plasma parameters and cathode performance is discussed to suggest design guidelines for the development of state-of-the-art hollow cathodes.

수평력을 받는 Plastic type PCV 밸브 내부 유동 가시화

PCV(Positive Crankcase Ventilation) system is designed to remove blowby gas. In this system, a PCV valve is attached in a manifold suction tube to control the flow rate of blowby gas which generates various operating conditions of an automotive engine. As this valve plays a crucial role, the demand in its design is high owing to the small size and high velocity. For this reason, a numerical investigation was carried out to understand both the spool dynamic motion and internal fluid flow characteristics. As a result, the spool dynamic characteristics(i.e. displacement, velocity, acting force), increase in direct proportion to the magnitude of the pressure difference and indicate periodic oscillating motions. Moreover, the velocity at the orifice region decreases according to the increase in differential pressure due to energy loss caused by the sudden decrease of flow area at the orifice region and the increase of flow volume in front of the spool head. Finally, the mass flow rate at the outlet decreases with the increase of spool displacement.

A biometric study of C‐shaped root canal systems in mandibular second molars using cone‐beam computed tomography

To investigate the configuration of C-shaped canals in mandibular second molars, canal wall thickness and the orientation of the thinnest area at 1-mm intervals from the canal orifice to the apex by using cone-beam computed tomographic (CBCT) images. Three-dimensional CBCT images of 92 Korean mandibular second molars having C-shaped root canals were analysed to determine their configuration using a modification of Melton's classification, as well as the thinnest walls and their location. Associations between configuration type and distance from the canal orifice to the apex, as well as associations between the directional orientation of the thinnest root wall and distance from the canal orifice to the apex, were assessed by Fisher's exact test. Because serial measurements of minimum wall thicknesses were correlated with individual teeth, a mixed-effects analysis was applied. The most common configuration types were Melton's type I in the coronal region and Melton's type III in the apical region. Mean thicknesses of the thinnest root canal walls were 1.39 ± 0.38, 0.85 ± 0.25 and 0.77 ± 0.20 mm in the coronal, middle and apical regions, respectively. The thicker the root canal walls at the orifice region, the greater the decrease in thickness towards the apical region (P < 0.05), with the linguo-central root area being the thinnest. The pattern of decreasing thickness from the orifice to the apex formed a nonlinear cubic curve. The most prevalent configuration types were Melton's type I (coronal region) and type III (apical region). The linguo-central root area was the thinnest in C-shaped root canals of Korean mandibular second molars. These anatomical variations should be considered during surgical or nonsurgical endodontic procedures.

Insights Into Coronary Artery Development in Model of Maternal Protein Restriction in Mice

Programming of fetal development is considered to be an important risk factor for noncommunicable diseases of adulthood, including coronary heart disease (CHD). Aiming to investigate the association between maternal nutrition and the development of the coronary arteries (CAs) in staged mice embryos, C57BL/6 mice embryos from Stages 16 to 23 were taken from mothers fed a normal protein (NP) or low protein (LP) diet, and the CA were studied. Although the LP embryos had lower masses, they had faster heart growth rates when compared with the NP embryos. The subepicardial plexuses were observed earlier in the NP embryos (Stage 20) than in the LP ones (Stage 22; P < 0.01). Apoptotic nuclei were seen around the aortic peritruncal ring beginning at Stage 18 in the NP and LP embryos. FLK1(+) (fetal liver kinase 1 = VEGF-r2 or vascular endothelial growth factor receptor 2) cells had a homogeneous distribution in the NP embryos as early as Stage 18, whereas a similar distribution in the LP embryos was only seen at Stages 22 and 23. Maternal protein restriction in mice leads to a delay in the growth of the heart in the embryonic period modifying the development of the subepicardial peritruncal plexus and the apoptosis in the future coronary orifice region.

1602 オリフィス下流域の乱流シミュレーション(OS16.エネルギー機器システムの設計・保守へのCFD適用,OS・一般セッション講演)

1602 オリフィス下流域の乱流シミュレーション(OS16.エネルギー機器システムの設計・保守へのCFD適用,OS・一般セッション講演)

Two-Dimensional FSI Simulation of Closing Dynamics of a Tilting Disk Mechanical Heart Valve

The fluid dynamics during valve closure resulting in high shear flows and large residence times of particles has been implicated in platelet activation and thrombus formation in mechanical heart valves. Our previous studies with bi-leaflet valves have shown that large shear stresses induced in the gap between the leaflet edge and the valve housing results in relatively high platelet activation levels whereas flow between the leaflets results in shed vortices not conducive to platelet damage. In this study we compare the result of closing dynamics of a tilting disc valve with that of a bi-leaflet valve. The two-dimensional fluid-structure interaction analysis of a tilting disc valve closure mechanics is performed with a fixed grid Cartesian mesh flow solver with local mesh refinement, and a Lagrangian particle dynamic analysis for computation of potential for platelet activation. Throughout the simulation the flow remains in the laminar regime and the flow through the gap width is marked by the development of a shear layer which separates from the leaflet downstream of the valve. Zones of re-circulation are observed in the gap between the leaflet edge and the valve housing on the major orifice region of the tilting disc valve and are seen to be migrating towards the minor orifice region. Jet flow is observed at the minor orifice region and a vortex is formed which sheds in the direction of fluid motion as observed in experiments using PIV measurements. The activation parameter computed for the tilting disc valve, at the time of closure was found to be 2.7 times greater than that of the bi-leaflet mechanical valve and was found to be in the vicinity of the minor orifice region mainly due to the migration of vortical structures from the major to the minor orifice region during the leaflet rebound of the closing phase.

Note: High temperature pulsed solenoid valve

We have developed a high temperature pulsed solenoid valve with reliable long term operation to at least 400 degrees C. As in earlier published designs, a needle extension sealing a heated orifice is lifted via solenoid actuation; the solenoid is thermally isolated from the heated orifice region. In this new implementation, superior sealing and reliability were attained by choosing a solenoid that produces considerably larger lifting forces on the magnetically actuated plunger. It is this property that facilitates easily attainable sealing and reliability, albeit with some tradeoff in attainable gas pulse durations. The cost of the solenoid valve employed is quite low and the necessary machining quite simple. Our ultimate level of sealing was attained by making a simple modification to the polished seal at the needle tip. The same sealing tip modification could easily be applied to one of the earlier high T valve designs, which could improve the attainability and tightness of sealing for these implementations.

Evidence of nonclassical plasma transport in hollow cathodes for electric propulsion

Measurements, simplified analyses, and two-dimensional numerical simulations with a fluid plasma model show that classical resistivity cannot account for the elevated electron temperatures and steep plasma potential gradients measured in a 25–27.5A electric propulsion hollow cathode. The cathode consisted of a 1.5cm hollow tube with an ∼0.28cm diameter orifice and was operated with 5.5SCCM (SCCM denotes cubic centimeter per minute at STP) of xenon flow using two different anode geometries: a segmented cone and a circular flat plate. The numerical simulations show that classical resistivity yields as much as four times colder electron temperatures compared to the measured values in the orifice and near-plume regions of the cathode. Classical transport and Ohm’s law also predict exceedingly high electron-ion relative drift speeds compared to the electron thermal speed (&amp;gt;4). It is found that the addition of anomalous resistivity based on existing growth rate formulas for electron-ion streaming instabilities improves qualitatively the comparison between the numerical results and the time-averaged measurements. Simplified analyses that have been based largely on the axial measurements support the conclusion that additional resistivity is required in Ohm’s law to explain the measurements. The combined results from the two-dimensional simulations and the analyses bound the range of enhanced resistivity to be 3–100 times the classical value.